1. Field of the Invention
The present invention relates to a discrimination sensor and a discrimination machine having a high accuracy and a high reliability to discriminate a specific object.
2. Description of the Related Art
Up until now, there have been proposed a wide variety of conventional discrimination sensor and conventional discrimination machine of this type one typical example of which is disclosed in the first patent document (Japanese Patent No. 2896288).
The conventional discrimination sensor disclosed in the first patent document is represented by reflection type to be disposed in face-to-face relationship with a distinctive characteristic segment of a planar structure (such as for example characters and figures printed on a bill) of a specific object (bill) when the specific object and the conventional discrimination sensor are relatively moved with respect to each other. In the above mentioned discrimination sensor of the reflection type, the data about the light reflected by the distinctive characteristic segment of the planar structure of the sample object (real bill) is previously stored as real samples. In the discrimination process, the determination is made on whether the specific object is real or fake by comparing the data (obtained by the characteristic segment when the bill is being moved with respect to the discrimination sensor) and previously stored data.
On the other hand, the conventional discrimination sensor of the transmission type is disclosed in the second patent document (Japanese Patent Laying-Open Publication No. 2003-77026).
In the above mentioned discrimination sensor of the transmission type, the data about the light transmitted through the distinctive characteristic segment of the planar structure of the sample object (real bill) is previously stored as a real sample. In the discrimination process, the determination is then made, in a way similar to the method identified in the first patent document, on whether the specific object is real or fake by comparing the data (obtained from the characteristic segment when the bill is being moved with respect to the discrimination sensor) and previously stored sample data.
In general, the above mentioned specific object, i.e., bills are mass-produced to have respective characteristic segments positioned with respective deviations which result in the printing precision and the mechanical accuracy of the printing machine. In the above mentioned conventional discrimination sensor, the data obtained from the displaced segments of the mass-produced bills are not always similar to one another by reason that each of the mass-produced bills is sensed in extremely narrow width by the conventional discrimination sensor.
In particular, the conventional discrimination sensor is disposed at a predetermined position. On the other hand, the conventional discrimination sensor is adapted to sense a segment of the specific object (bill) in a predetermined scanning direction under the condition that predetermined position of the conventional discrimination sensor is not adjusted on the basis of the deviation of the characteristic segment. This means that the data obtained from the sensed segment of the specific object (bill) is not always the same as the previously stored sample data under the condition that the characteristic segment is positioned with a deviation.
The conventional discrimination machine thus constructed as previously mentioned, however, encounters such a problem that the deviation may lead to the fact that the conventional discrimination sensor is operated to sense a segment (spaced apart from the characteristic segment) different from the characteristic segment by reason that the specific object (bill) is sensed in extremely narrow width under the condition that the characteristic segment is positioned with a deviation. This means that the real object (real bill) may be erroneously determined as a fake object (fake bill) by comparing the sample data and the data obtained from the segment different from the characteristic segment on the supposition that the characteristic segment is sensed by the conventional discrimination sensor. This leads to the fact that the accuracy and the reliability of the discrimination is deteriorated by the deviation of the characteristic segment.